1. Field of the Invention
The present invention relates to a planer light source device using a light source.
2. Description of the Related Art
A planer light source device, for example, a planer light source device of a non-emissive display device such as a liquid crystal display, has a side light type (also called an edge light type) and a direct type. The planer light source device of the side light type has a light source disposed on the side face of a rear frame, whereas the planer light source device of the direct type has a light source disposed on the rear face of the rear frame opposed to a display part.
Also, the planer light source device of the side light type includes a light guide plate for guiding the light from the light source in a desired direction, in which the light emitted from the light source including a linear light source such as a Cold Cathode Fluorescent Lamp (hereinafter referred to as CCFL) or a point light source such as a Light Emitting Diode (hereinafter referred to as LED) is reflected within the light guide plate and diffused with a diffusion pattern provided within the light guide plate to direct the light at a display screen.
Further, a middle frame is disposed for sandwiching the light guide plate with the rear frame. A display panel is provided on the screen side of the light guide plate. A front frame that supports the display panel, the middle frame and the rear frame and has an opening is disposed on the screen side of the display panel.
In the planer light source device, a step portion is provided on the side face of the middle frame, and a claw portion provided on the rear frame is fitted into the step portion of the middle frame to fix the middle frame and the rear frame together.
Also, in the planer light source device (e.g., see JP-A-2002-40394), a window is provided in an engagement piece of a back face frame in contact with the side face of an intermediate frame, and engaged by a projection provided in the intermediate frame to fix the intermediate frame and the back face frame.
However, it is required to provide the step portion or projection on the side face of the middle frame, so that the thickness of the side face of the middle frame is increased. Also, since the side face of the middle frame and the side face of the rear frame overlap, the planer light source device has a wider frame area (wider peripheral area of the frame of the display screen).
Further, the peripheral portion of the light source is heated to high temperature due to heat generated from the light source, which cases the emission light flux of the light source to be lower and results in a problem that the light source is degraded in the life and reliability. Thus, there is a demand that the contact area between a lamp reflector and the rear frame is increased, whereby it is difficult to provide a fixing structure of the middle frame and the rear frame, which results in a problem that a movement occurs due to vibration or shock.
Also, in JP-A-2002-40394, since the projection provided in the intermediate frame is not overlaid on the side face of a reflective sheet, the positional regulation of the reflective sheet could not be made when the planer light source device is assembled from the intermediate frame.